When booting a new instance in Genostack, you are given the choice between two sources: Images, or Volumes.
While the behaviour of the instance itself will not be affected by the type of source, there is a major difference in data persistence
Using an image as a source
When you boot from an image, you will get the same instance it was at the time of the snapshot. Booting 10 instances will produce the same result every time.
Booting from an image is better if you want to have a clean environnement for repeatability.
If you wish to save the state of your instance, you will need to create a snapshot of it, and use it as an image when you boot a new instance.
Using a volume as a source
When you boot from a volume, the instance will be in the same state as you left it the last time you used the volume. Any modification you make on it will be saved in real-time.
Booting from a volume is better if you want to keep working on the same instance while saving your changes.
There is no need to save the state of your instance, you can boot from the same volume later.